Self-starting single-phase motor and its control



Nov. 18, 1941. a G, VEINOTT TA 2,262,870

SELF-STARTING SINGLE-PHASE MOTOR AND ITS CONTROL Filed April 13, 1940INVENTORS fi Cyril 6'. 142272012 and Q/endeil 6f Spear:

ATTORNEY Patented Nov. 18, 1941 SELF-STARTING SINGLE-PHASE MOTOR AND ITSCONTROL Cyril G. Veinott, Lima, and Wendell C. Spear, Wapakoneta, Ohio,assignors to Westinghouse Electric & Manufacturing Company, EastPittaburgh, Pa., a corporation of Pennsylvania Application April 13,1940, Serial No. 329449 22 Claims.

Our invention relates to self-starting singlephase induction-motors, andto novel and improved means for starting the same, and also novel andimproved means for delaying the starting of thesame.

An object of our invention relates to the-provision of a motor of theclass described, having two complete, inductively related main-windingswhich are adapted to be connected, at times, in

be symbolic 01' any starting winding-means which, in general, may beregarded as comprising a winding disposed in substantiallyquadraparallel, and a quadrature-related. dephasedloture space-relationto the main windings I and current, starting winding-means. with novel6, and adapted to have a current out of phase connections for startingthe motor by applying with the current in the main windings.line-voltage to only cheer the' main windings The motor is also providedwith a secondary and utilizing the other main winding to energize orrotor-member ll which is provided with a the starting winding-means.After the motor squirrel-cage winding H or other poly-axially hasattained a suflicient speed, the two main short-circuited secondarywinding. The rotorwindings may be connected in parallel across themember II is mounted on a shaft 12 which carsupply-line, either with, orwithout, the deenerries a centrifugal device or speed-governor I3gization of the starting winding-means. which operates a start-runswitch It having two A further object of our invention relates toback-contacts l5 and I 6 and one irontcontact the delayed starting of athree-winding motor or make-contact l'l. of the type just described,whereby the motor is The motor is also provided with a time-delayinitially energized by applying the line-voltage starting-means hich 15illustrated -8 06 8 n to only one ofthe .two main windings, in comheform of a curr nt-resp nsiv swi hingedebination with novel control-meanswhereby startvice which is illustrated in the form of a motoring isdelayed, and at the same time the noiseunted ther al y r sp nsiv sw tc i-m ans hum is practically eliminated, and th r t r- 20 having abimetallic switch-contact element 2| heating is very materially reduced,by providing and a heatinl resistance 21 p e in di e a.closed-circuiting path which close-circuits both heatingsl'elltion 0 thebimetallic -elethe'second main winding and the starting windmerit Thebimetallic contacts 2 are 110 ing-means. Starting is thereafter effected,by a y c ed a are a p to open automatthe time-delayed opening of theclosed-circuiting c y when the thermally responsive itc ngpath. means 20is heated to a predetermined tempera- With the foregoing and otherobjects in view, tu a th r by the heat P d in the heatingvour inventionrelates to the apparatus, methods, resistance 22 01' the thermallyresponsive c combinations and systems hereinafter described y eat w ic sd ec a d t0 t e therand claimed, and illustrated in the accompanymallyresi device from the motor wh fi 8 ing drawing, wherein: beingcontrolled. As schematically illustrated in Figures 1, 2 and 3 arediagrammatic views 01 the w the thermally r ponsive device 20 circuitsand apparatus embodying our invention 40 is disposed in juxtapositionthe motor. 0 that in three different illustrative forms of embodiit isin direct heat-transfer relation thereto, bement thereof, ing usuallymounted on the stator element which In Figure l, we illustrate ourinvention as apcarries the three windings 3 d plied to a single-phaseinduction motor having The m I 1S 8180 Provided w o ne-tera primarymember or stator element carrying 111111818 13 and N which a e apted tobe enertwo main windings 5 and 6 and an auxiliary S from s -Dhase lineL, as by means starting-winding l. The two main windings I of aline-switch 25 in one of the line-terminals and 6 are substantially inspace-phase with each other, and preferably each of the two main wlnd-One of the w main windin s, such as theingsisacomplete winding, withwinding-portions winding 5, has its terminals connected to the disposedon, or for, each pole of the motor, the two l n mihflls 23 and p y- Incorresponding winding-portions or the two main the particular form ofembodiment shown in windings being mutually coupled to each other, Fig.1, the other main winding 6 has one terminal preferably by being woundin the same slots. connected to the line-terminal 23, and the other Theauxiliary starting-winding is illustrated, terminal connected to themovable switch-arm ll of the speed-responsive device. The auxiliarystarting-winding 1 is connected, in series with its phase-shiftingcapacitor 8, between the lineterminal 23 of the back-contact I6 which isin engagement with the centrifugal switch It in the starting position ofthe latter. The heating element 22 and the terminal contacts 2|- of thethermally responsive device 20 are connected in series with each otherin a short-clrcuiting or closed-circuiting circuit extending from thelineterminal 23 to the back-contact l5 which is in in Fig. 1, as byclosure of the line-switch 25, the

first main-winding 5 is immediately energized, and the secondmain-winding 6 has voltage inin connecting the second main-winding 6 inparallel with the first main-winding 5, across the line-terminals 23 and2. At thesame time, the starting winding-means 18 is altogetherdeenergized, although this feature is not a necessary part of myinvention. It is noted, also, that theactuation of the centrifugalswitch-arm l4 to its running position results in open-circuit'ing theclosed-circuit path 2|-22 at the back-contact I5, so that, when thebimetallic switchcontacts 2| subsequently reclose, as they will do,

after a certain period of time, as a result of the cooling of thethermally responsive device when its heater 22 is deenergized, thereclosure of these bimetallic contacts 2| will not result in againshort-circuiting either the main winding 6 or the auxiliarywinding-means 18, as long duced therein by transformer action from thefirst main-winding 5. The second main-winding 8 is connected, throughthe switch-arm II and the back-contact IE, to the closed circuit 2l-22which provides a fairly low-impedance path connected across theterminals of the second mainwinding 6, so that very little voltageappears thereacross. Tests have shown that the current flowing in thisclosed circuit 2|-22 under these conditions is a moderate current whichthe stator element of the motor can easily withstand for a limited time.The second main-winding 8 is also connected, through the switch-arm l4and the back-contact It, to the auxiliary starting winding-means 10, butthe latter receives a voltage which is far too low to cause a startingoperation of the motor, as long as the bimetallic switchcontact 2| isclosed in the closed-circuit 2|22 which is connected both across theterminals of the second main-winding 8 and across the terminals of theauxiliary winding-means l-l.

As soon as the line-terminals 23 and 24 are energized, therefore, amoderately large current begins to flow in the closed-circuiting pathincluding the closed contacts 2| and the heating resistance 22 "of thethermally responsive device 2|). After an elapse of a predeterminedtime, for

which the thermally responsive device 20 is adiusted, the heater 22heats the bimetallic strip or disc 2| to a suflicient extent to causethe switch-contacts to snap open, thereby removing the closed-circuitpath from across the terminals of the second main-winding 6 as well asfrom across the'terminals of the auxiliary starting winding-means'1-8.This immediately causes the transformer- 'voltage induced in the secondmain-winding 8 to be applied to the starting winding-circuit 18, thusimpressing, on the as the centrifugal switch-arm I4 is in its runningposition in engagement with the front-contact II. The closed-circuitingpath which is provided by the elements 2| and 22 of the thermallyresponsive device 20, in the circuits hereinabove described, and shownin Fig. 1, serves several important functions, which will be mentioned,not necessarilyin the order of their merit.

When only one of the two normally parallelconnected windings 5 and 6 isenergized, the current is limited by the resistance of the primary androtor windings, and by the leakage-reactance of both the primary and therotor. Under such conditions a large current flows in the rotor; as iswell known to the art, this current, referred to the primary, issubstantially the same as the stator current, that is, large. Togenerate sufllcient voltage in the rotor to overcome to thevoltage-drops due to rotor-resistance and leakage- -reactance, aconsiderable amount of flux must traverse the air-gap. Theamount of fiuxcrossing the air-gap of a motor as previously constructed, underlocked-rotor conditions, may be i from one third to two thirds of thenormal airgap flux at no load or running light. With-this picks up andamplifies this hum to objectionable proportions.

One of the objects of our invention is to eliminate this hum during thedelay-period while the starting winding-circuit, a voltage which is.

nearly as large as the full line-voltage, or at least sumciently closelyapproximating the linevoltage to produce a starting-operation of themotor. The voltage impressed on the startingwinding circuit 18 isapproximately in phase with the line voltage, just as, the secondaryvoltage of a transformer is approximately in phase with the primaryvoltage.

When the motor achieves a certain predetermined percentage of itsrunning-speed, the centrifugal governor ll actuates the switch-arm H soas to disengage the back-contacts II and I6 and engage the front-contactII, which results terminals 23 and 24 are energized, and before thethermally responsive switching means 20 opens. During this periodweenergize only one of the two normally parallel-connectedmainwindings iand i, and we short-circuit the mainwinding 6. The short-circuit currentin the winding-section 6 is nearly equal to the current in thewinding-section 5, and thus the two windings oppose each other, leavingsubstantially no flux to cross the air-gap. When practically no fluxcrosses the airgap, the -cycle hum is strikingly reduced.

While we are not limited to any particular magnitudes, it may bementioned, as giving some indication of the order of improvementexpectable, that the change from energizing both sections 5 and 6 of themain-winding, in parallel, from the line-voltage, to energizing only oneof these sections and short-circuiting or closed-circuiting.the othersection, resulted in a reduction of the noise, in one particularinstance, from 56 decibels to 29 decibels, corresponding to a reductionin" loudness, to the human ear, in the ratio'of approximately 10 to 1.or a reduction in the acoustic energy in the ratio of approximately 500to 1. This reduction in the magnetic hum is particularly important inunit-heater installations in which there is a large quantity ofsheetmetal which serves as a sounding board for picking up andintensifying the noise.

As mentioned before, our reduction in the motor-flux during thetime-delay period, when the motor is energized but is not permitted tostart, is also important in considerably reducing the flux which reachesthe secondary member II of the motor, thus resulting in a veryconsiderable reduction in the heating of the secondary member duringthis time-delay period. This reduction in the temperature of thesecondary or rotor-member of the motor may be so great, in someinstances, as to permit the use of a softsoldered rotorinstead of abrazed or indestructible rotor, thus offering a material advantage fromthe standpoint of cost.

Another ad antage of the utilization of our closed-circuiting path2|--22 is that it makes use of a standard type of closed-contactthermostatic disc-switch, utilizing a bimetallic dished disc-elementhaving contacts which are closed in the cold position of the switch, asdistinguished timing device, and producing a simpler and neatermotor-combination.

Our invention is, of course, not limited to the particular form ofembodiment shown in Fig. 1.

from a thermostatic switch having normally open contacts, or contactswhich are open when the switch is cold.. This is a desirable feature,from a practical standpoint, because there are already developed, andavailable on the market, number of thermostatic snap-action switcheshaving normally closed contacts, in a range of sizes and ratings whichare suitable for the purpose at hand, whereas the utilization of athermostatic switch having normally open contacts would, as a practicalmatter, require the developmentof a special thermostatic switch, whichwould not only entail certain costs, in its development, but which wouldalso lack the quantityproduction advantages which are derived fromutilizing a standard switch of a type which already has a number ofother commercial uses.

Our utilization of a thermostatic time-delay switch which is responsive,not only to the heating of its own heating-element 22, but which is alsoin direct heat-receiving relation to the motor itself, or to someportion of the stator-member of the motor, has the important practicalresult of causing the time-delay period to be variable in accordancewith the initial temperature of the motor, because it will take ashorter time for the heating element 22 to raise the bimetallic switch2| to its critical temperature when the motor is hot, than when themotor is cold. desirable feature, because it likewise takes a shortertime to heat up the heater, when the heater is initially warm, than whenthe heater is initially cold. Our placement of the thermally responsivetime-delay element 20 in heat-conducting relation to the motor is,therefore, a valuable means for achieving a time-delay period which isinherently and automatically variable in a desired manner.

It will be further noted that our utilization of a so-called internaltime-delay switching-element 2!), or an element which is built into themotor itself, as distinguished from an external time-delayingswitching-device, has an advantage in installation and wiring costs, aswell as an advantage from the standpoint of simplicity and neatness ofappearance, thus avoiding the expense of separately mounting, and makingthe electrical connections to and from, an external In unit-heaterapplications, this is a most By way of suggestion as to some of thepossibilities of variations in design, we have shown, in Fig. 2. a motorin which the starting-winding 21 is a split-phase winding rather than acapacitorwinding, the split-phase winding having inherently such ratioof resistance to inductance as to cause the current therein to bedephased with respect to the current in the main-windings 5 and 6.

In Fig. 2, also, the second main-winding 6, which serves as atransformer-secondary during the initial time-delay period, as well aduring the relatively brief, subsequent, starting-period, is providedwith a serially connected external resistor 28, which is shown as beingconnected between the winding 6 and the centrifugal switcharm II; andthe centrifugal switching device is provided with a second make-contact29, which is engaged by the switch-arm M in the running position of theswitch, and which is utilized to short-circuit the auxiliary resistor28. This auxiliary resistor 28, during the initial time-delay which isprovided by the thermally responsive device 20, serves to somewhatreduce the magnitude of the current flowing in the closed-circuitingpath 282l--22; while at the same time the lower-resistance circuit2l--22 practically'shortcircuits the auxiliary starting-winding 21 andprevents the application of voltage to the latter. During thestarting-period, before the bimetallic snap-switch 2| has opened, theauxiliary resistor 28 is in series with the split-phase starting-winding21, which is, in many cases, an advantage in assisting in dephasing thestarting-winding current as compared with the currents in themainwindings 5 and 6.

In Fig. 3, we show a somewhat modified-wiringdiagram which sometimeslends itself to less critical adjustment of the timing of the thermalelement 20 with respect to the characteristics of the motor which is tobe controlled. In said Fig. 3, the thermal device is designated by thenumeral 20, and it is provided with a heating-resistor 22' which isserially connected with the motor-terminal 23, so that it is traversedby the entire input-current of the motor, rather than simply by theshort-circuit current of the second mainwinding 6. As in the previouslydescribed figures, the bimetallic contact-element 2| of the thermaldevice 20' is connected in series with the centrifugal switch-members I4--l5, and across the terminals of the second main-winding 6. Except forthe recalibration of the thermal device 20', the operation of theembodiment of our invention shown in Fig. 3 is essentially the same asthat which has previously been described.

I While we have illustrated our invention in three diflercnt forms ofembodiment, which are at present preferred by us, we desire it to beunderstood that our invention is not limited thereto, as many changesmay be made by the skilled workers of the art, by way of additions,substitutions and Omissions, without departing from the essential spiritof our invention, particularly in its broader aspects. We desire,therefore, that the appended claims shall be accorded the broadestconstruction consistent with their language and the prior art.

We claim as our invention:

1. A delayed-start, single-phase motor having two main winding-meanssubstantially in spacephase with each other, said two main windingmeansbeing disposed in mutually inductive transformer-relation to each other,and a substantially quadrature-related starting windingmeans of a typeadapted to have current out of .phase with the current in the mainwinding-- means, a pair of line-terminals connected to a first one ofthe main wlnding-meanameans for initially providing a closed circuit forthe second main winding-means and for initially causing the startingwinding-means to be de-energized to such an extent that starting doesnot ensue when single-phase electrical energy is first applied to theline-terminals, and time-delayed current-responsive means, responsive toa predetermined current in said motor, for interposing a time-delayafter the application of electrical energy to the line-terminals and forsubsequently opening said closed circuit and causing the startingwinding-means to be energized from said second main winding-means.

,2. A delayed-start, single-phas motor having two main winding-meanssubstantially in spacephase with each other, said two main windingmeansbeing disposed in mutually inductive transformer-relation to each other,and a substantially quadrature-related starting windingmeans of a typeadapted to have current out of phasewith the current in the mainwindingmeans, a pair of line-terminals connected to a first one of themain winding-means, means for initially providing a closed circuit forthe second main winding-means and for initially causing the startingwinding-means to be de-enersizcd to such an extent that starting doesnot ensue when single-phase electricaleeilergy is first applied to theline-terminals, time delayed current-responsivemeans, responsive to apredetermined current in said motor. for interposing a time-delay afterthe application of electrical energy-to the line-terminals and forsubsequently opening said closed circuit and causing thestartingwindingmeans'to be energized from said second main aasasvosecond main winding-means across the line-terminals in parallel to saidfirst main windingmeans.

4, A delayed-start, single-phase motor having two main winding-meanssubstantially in spacephase with each other, said two'rnain windingmeansbeing disposed in mutually inductive transformer-relation to each other,and a sub.- stantially quadrature-related starting windingmeans or atypeadapted to have current out at phase with the currenti'in the.winding-- means, a pair of line-terminals connected to a first one ofthe main winding-means, means for initially providing a closed circuitfor the second main winding-means and for initially causing the startingwinding-means to be de-energized to such an extent that starting doesnot'ensue when singlephase electrical energy is first applied to theline-terminals, timedelayed currents responsive means; responsive to apredetermined current in said motor, for interposing a time-- delayafter the application or electrical energy transformer-relation to eachother, and a substantially quadrature-related starting windingmeans of atype adapted to have current out 01' phase with the current in the mainwinding means, a pairoi line-terminals connected to a first one of themain winding-means. and a' thermally responsive switch having initiallyclosed winding-means, whereby the motor starts, and

start-run switching-meana perable after the motor has started, forenergizing said second main winding-means'across the line-terminals inparallel to said first main winding-means.

3. A delayed-start. single-phase motor having two main winding-meanssubstantiallyin spacephase with each other, said two main windingmeansbeingdisposed in mutually inductive transformer-relation to each other,andasubstantially quadrature-related starting winding means .of atypeadapted to have current out or phase with the current in the mainwindingmeans, a pair of line-terminals connected to a first one 0! themain winding-means, meansior initially providing a closed circuit forthe second main windingemeans and for initially causing the startingwinding-means to be de-energized to such an extent that starting doesnot ensue when single-phase electrical\ energy is first applied to theline-terminals, time-delayed current-responsive means, responsive to apredetermined current in said motor, for interposing a time-delay afterthe application of electrical energy to the line-terminals and forsubsequently opening said .osed circuit and causing the startingwinding-'- mearis to be energized from said second main 7 winding-means,whereby the motor starts. and

start-run switching-means, operable alter the said contacts initiallyconnected in closed-circuiting relation across both the secondmainwindingmeans and the starting winding-means, said thermally responsiveswitch being located in direct heat-receiving relation to said motor andalso having an electrically energized heatinselement of its own, saidthermally responsive switch operating, after a time-delay after theapplication of electrical energy to said line-terminals, to open itscontact, thereby causing said starting winding-means to be eflectivelyenergized from said second main winding-means so as to start the motor.

6. A delayed-start, single phase motor'having two main winding-meanssubstantially in spacephase with each otherysaid two main windingmeansbeing disposed in mutually inductive transformer-relation to each other.and a substantially quadrature-related starting windingmeans of a typeadapted to have current out oi phase with thevcurrent in the mainwindingmeans, a pair or line-terminals connected to a first one of themain winding-means, a thermally motor has started, for causing saidsecond main winding-means to be disconnected from said.

responsive switch having initially closed contacts initially connectedin closed-circuiting relation across both the second main winding-meansand the starting winding-means, said thermally responsive switch beinglocated in direct heatreceiving relation to said motor and also havingan electrically energized heating-element of its own, said thermallyresponsive switch operating.

after 'a time-delay after the application of eleccontact, therebycausing said starting windingmeans to be efiectively energized from saidsecond main winding-means so as to start the motor, and start-runswitching-means, operable after the motor has started, for energizingsaid second main winding-means across the line-terminals in parallel tosaid first main winding-means.

7. A delayed-start, single-phase motor having two main winding-meanssubstantially in spacephase with each other, said two main windingmeansbeing disposed in mutually inductive transformer-relation to each other,and a substantially quadrature-related starting windingmeans of a typeadapted to have current'out of phase with the current in the mainwindingmeans, a pair of line-terminals connected to a first one of themain winding-means, a thermally responsive switch having initiallyclosed contacts initially connected in closed-circuiting relation acrossboth the second main winding-means and the starting winding-means, saidthermally responsive switch being located in direct heat-receivingrelation to said motor and also having an electrically energizedheating-element of its own, said thermally responsive switch operating,after a time-delay after the application of electrical energy to saidline-terminals, to open its contact, thereby causing said startingwindingmeans to be effectively energized from said second mainwinding-means so as to start the motor, and start-run switching-meansoperable after the motor has started, for causing said second mainwinding-means to be disconnected from said starting Winding-means andfor energizing said second main winding-means across the line-terminalsin parallel to said first main windingmeans.

8. A delayed-start, single-phase motor having two main winding-meanssubstantially in spacephase with each other, said two main windingmeansbeing disposed in mutually inductive transformer-relation to each other,and a sub- -stantially quadrature-related starting windingmeans of atype adapted to have current out of phase with'the current in the mainwindingmeans, a pair of line-terminals connected to a first one of themain winding-means, a thermally responsive switch having initiallyclosed contacts initially connected in closed-circuiting relation acrossboth the second main winding-means and the starting winding-means, saidthermally responsive switch being located in direct heat-receivingrelation to said motor and also having an electrically energizedheating-element of its own, said thermally responsive switch operating,after a time-delay after the application of electrical energy to saidline-terminals, to open its contact,

thereby causing said starting winding-means to be effectively energizedfrom said second main winding-means so as to start the motor, andstart-run switching-means, operable after the motor has started, forsubstantially open-circuiting said starting winding-means and forenergizing said second main winding-means across the line-terminals inparallel to said first main winding-means.

9. The invention as defined in claim 1, characterized by said two mainwinding-means each having corresponding mutually coupled windingportionsfor each pole of the motor.

10. The invention as defined in claim 2, characterized by said two mainwinding-means each having corresponding mutually coupled windingportionsfor each pole of the motor.

. trical energy to said line-terminals, to open its 11. The invention asdefined in claim 4, characterizedbysaid two main winding-means eachhaving corresponding mutually coupled windingportions for each pole ofthe motor.

12. The invention as defined in claim 5, characterized by said two mainwinding-means each having corresponding mutually coupled windingportionsfor each pole of the motor.

13. The invention as defined in claim 6, characterized by said two mainwinding-means each having corresponding mutually coupled windingportionsfor each pole of the motor.

14. The invention as defined in claim 8, characterized by said two mainwinding-means each having corresponding mutually coupled windingportionsfor each pole of the motor.

15. A delayed-start, single-phase motor having two main winding-meanssubstantially in spacephase with each other, said two main windingmeansbeing disposed in mutually inductive transformer-relation to each other,and a substantially quadrature-related starting windingmeans, a pair ofline-terminals connected to a first one of the main winding-means, aphasecontrolling impedance-device connected in a circuit seriallyincluding the second main windingmeans and said starting winding-means,means including normally closed switching-means for initially providinga closed circuit directly across the terminals of said startingwinding-means, and time-delayed current-responsive means, responsive toa predetermined current in said motor, for opening said switching-means,thereby interposing a time-delay in the energization of the startingwinding-means after the application of electrical energy to theline-terminals and for subsequently opening said closed circuit.

16. A delayed-start, single-phase motor having two main winding-meanssubstantially in spacephase with each other, said two main windingmeansbeing disposed in mutually inductive transformer-relation to each other,and a substantially quadrature-related starting windingmeans, a pair ofline-terminals connected to a first one of the main winding-means, aphasecontrolling impedance-device connected in a circuit seriallyincluding the second main windingmeans and said starting winding-means,means including normally closed switching-means for initially providinga closed circuit directly across the terminals of said startingwinding-means, time-delayed current-responsive means, responsive to apredetermined current in said motor, for opening said switching-means,thereby interposing a time-delay in the energization of the startingwinding-means after the application of electrical energy to theline-terminals and for subsequently opening said closed circuit, andstart-run switching-means, operable after the motor has started, fordisconnecting said im-. pedance-device and said starting winding-meansfrom said second main winding-means and for energizing said second mainwinding-means across the line-terminals in parallel to said first mainwinding-means.

17. A delayed-start, single-phase motor having two main winding-meanssubstantially in spacephase with each other; said two main windingmeansbeing disposed in mutually inductive transformer-relation to each other,and a substantially quadrature-related starting windingmeans, a pair ofline-terminals connected to a first one of the main winding-means, aphasecontrolling impedance-device connected in a circuit seriallyincluding the second main windingsponsive switch beinglocated in directheat=receiving relation to said motor and also havin an electricallyenergized heating-element of its own, said thermally responsive switchoperating, after a time-delay after the application of electrical energyto said line-terminals, to open its contact.

18. A delayed-start, single-phase motor having two main winding-meanssubstantially in spacephase with eachother, said two main windingmeansbeing disposed in mutually inductive transformer-relationto each other,and a substantially quadrature-related starting windingmeans, a pair ofline-terminals connected to a first one of the main winding-means, aphasecontrolling impedance-device connected in a circuit seriallyincluding the second main windingmeans and said starting winding-means,a thermally responsive switchhaving'initially closed contacts initiallyconnected in closed-circuiting relation directly across the terminals ofsaid starting winding-means, said thermally responsiveswitch beinglocated in direct heat-receiving relation to said motor and also havingan electrically energized heating-element of its own, said thermallyresponsive switch operating, after a time-delay after the application ofelectrical energy to said line-terminals, to open its contact, andstart-rim switching-means, operable after the motor has started, fordisconnecting said impedance-device and said starting windingmeans fromsaid second main winding-means and for energizing said second mainwinding- 10. means across the line-terminals; in parallel to said firstmain winding-means.

19. The invention as defined in claim 15, characterized by said two mainwinding-means each having corresponding mutually coupled windingportionsfor each pole of the motor.

20. The invention as defined in claim 16, characterized by said two mainwinding-mea'nseach having corresponding mutually coupled winding- 22.The invention as defined .in c1aimt18, characterized by said two mainwinding-means each having corresponding mutually coupled windingportionsfor each pole of the motor.

CYRIL Gr VEINO'IT. WENDELL C. SPEAR.

